<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <botton id="btn">登录</botton>
    <script>
      //获取按钮
      //1.通过id获取 document.getELementByid(选择器)
      var btn = document.getElementById('btn');

      console.log(btn);
      //检测一下类型是不是对象
      console.log(typeof btn); // object  (对象)

      document.getElementById;
    </script>
  </body>
</html>
